1. Field of the Invention
The present invention relates generally to signal lights and illumination. In particular, the present invention relates to directional light sources (lamps) such as a parabolic aluminum reflector (PAR) type, metallized reflector (MR) type, reflector (R) type and the like.
2. Discussion of the Related Art
Lighting device efficiency has always been a major factor in light source evaluation. Efficiency is measured by the portion of all generated light that is useful for a given application (e.g., to illuminate a given area with a given illuminance). Most conventional light sources (incandescent, halogen, fluorescent, high discharge, high pressure, etc.) by their nature are almost omnidirectional sources in that they emit light in all directions.
For applications that require light distribution in limited angles or area, the conventional light sources are typically used in combination with reflectors that collect and direct the light generated by the source.
It is well known that these systems are not very efficient. For example, medium approach lighting systems for airplane landings require an average intensity of 10,000 candelas in an area 20xc2x0 in horizontal by 11xc2x0 in vertical that results in a total luminous flux of approximately 300 lm. For this application, PAR-38 100 watt lamps are typically used that emit approximately 1,500 lm. Unfortunately, efficiency of this type of lamp in this type of application is approximately 20%.
A new generation of lighting devices is based on solid state technology. In addition to other benefits, light emitting diodes (LEDs) have higher efficiency in that they produce more light per watt and they have an extremely long life. Recent advances have taken place in the area of directional LED lamp construction.
One of the basic categories of LED lamp construction is the implementation of multiple LEDs in a cluster to combine luminous flux from multiple LEDs using primary optics integrated in the LED for directionality. LED manufacturers offer a wide choice of primary optics including from 120xc2x0 to 5xc2x0 directionality.
Unfortunately, higher directionality correlates to higher losses in the primary optics. For example, LEDs having the same chip in a 5 mm diameter green Nichia LED(trademark) (NSPG-5 series) has a total luminous flux of 1.46 lm with a 45xc2x0 lens, 1.2 lm with a 30xc2x0 lens, and only 0.7 lm with a 15xc2x0 lens. Consequently, using primary LED optics results in an inefficient LED lamp design.
The other basic category of construction of LED lamp design is based on the use of an additional optical element (a xe2x80x9csecondary opticxe2x80x9d) to concentrate and direct the light (e.g., implementation of a refractive lens, using a reflector as a secondary optic, etc.).
Unfortunately, none of the current designs based on the use of LEDs in combination with conventional optics (refractive or reflective) provides high efficiency performance because almost all conventional optic designs are based on the xe2x80x9cpoint sourcexe2x80x9d concept with the assumption that the light source has a negligible physical size which is work for low power LEDs typically having a lighting body tens to hundreds of microns.
With the tendency of the LED technology to reach high power, the physical size of the LED chips are becoming much larger. For example, Lumelid""s Luxeon Star(trademark) 1 watt LED has a chip that is 0.5xc3x970.5 mm and Luxeon Star(trademark) 5 watt is 2.0xc3x972.0 mm2. Increasing light source size with the use of conventional optics creates a sufficient aberration, resulting in large losses and low efficiency.
What is needed, therefore, to overcome these limitations found in conventional systems is the application of solid-state technology (e.g., light emitting diodes) using nonimaging optics (NIO) as a secondary optic.
The present invention includes a highly efficient LED lamp based on the use of a high power LED as a light source in combination with a non-imaging optical element as a secondary optic. Multiple LEDs can also be used in combination with the non-imaging optical elements to provide specific spatial light distribution. The lamp can also include a light shaping element and an adapter/converter for conventional lamp replacement.
In particular, the present invention provides a highly efficient LED lamp including an optical module and a housing. The optical module includes at least one light emitting diode (LED) that emits light with a wide divergence and a non-imaging optical element (NIO). The NIO includes a refractive member located around a LED optical axis and a total internal reflection member located around the refractive member, wherein the refractive member and the total internal reflection member are integrated in a single transparent element having a mutual focal point, wherein the NIO element collects a significant amount of light emitted by the LED with wide divergence located at the focal point, to compress the collected light with high efficiency into a beam with a generally different angular spread in a horizontal plane and a vertical plane and to direct the compressed light outside of the lamp. A transparent window transmits light outside of the lamp. A housing includes an electrical connector connected to an outside power source, and the connector is electrically connected to the LED.
According to one aspect of the invention, an optical module includes at least one light emitting diode (LED) that emits light with a wide divergence. A non-imaging optical element (NIO) includes a refractive member located around a LED optical axis and a total internal reflection member located around the refractive member, wherein the refractive member and the total internal reflection member are integrated in a single transparent element having a mutual focal point, wherein the NIO element collects a significant amount of light emitted by the LED with wide divergence located at the focal point, to compress the collected light with high efficiency into a beam with a symmetrical angular spread in a horizontal plane and a vertical plane. A transparent window transmits shaped light outside of the lamp, wherein the NIO element directs the compressed light towards the transparent window. A light shaping element is located between the non-imaging optical element and the transparent window.
According to yet another aspect of the invention, a highly efficient LED lamp includes an optical window having at least one light emitting diode (LED) that emits light with a wide divergence. A non-imaging optical element (NIO) includes a refractive member located around a LED optical axis and a total internal reflection member located around the refractive member, wherein the refractive member and the total internal reflection member are integrated in a single transparent element having a mutual focal point, wherein the NIO element collects a significant amount of light emitted by the LED with wide divergence located at the focal point, to compress the collected light with high efficiency into a beam with a generally different angular spread in a horizontal plane and a vertical plane, and to direct the compressed light outside of the lamp. A transparent window transmits the light outside of the lamp. A housing has an electrical connector connected to an outside power source. An electronic adapter/converter is mounted to the housing, and the adapter/converter has an electrical input and an electrical output, wherein the electrical input is connected to the electrical connector in the housing and the electrical output is connected to the LED.
These and other objects, features, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.